The present invention relates to an apparatus for changing a convolution circle or turned diameter of a cutting edge of a lathe tool of a machine tool.
It has been proposed to change the convolution circle of a lathe tool of a machine tool by a hydraulic or mechanical adjusting device; however, disadvantages of these proposals reside in the fact that there is a tendency for the machine tool to become unadjusted or misaligned due to centrifugal forces so that the proposed systems become unstable at rotational speeds of less than 10,000 rpm. Moreover, from a constructional point of view, it is especially difficult to accommodate the proposed systems with decreasing rotating diameters since they cannot be arranged in the tool or the like.
The aim underlying the present invention essentially resides in eliminating the disadvantages encountered in prior proposals by providing a method for changing a position of a cutting edge of a lathe tool of a machine tool arrangement that can be carried out in a simple manner, while nevertheless ensuring a high degree of accuracy at high rotational frequencies or speeds.
Another aim of the present invention essentially resides in providing an apparatus for applying the method of the present invention not only for internal but also for external machining of workpieces.
In accordance with the advantageous features of the method of the present invention, it is possible to alter a convolution circle or turned diameter of a cutting edge of a lathe tool of a machine tool by carrying out an adjustment in dependence upon at least one of a rotational frequency and a centrifugal force acting thereon.
By virtue of the features of the method of the present invention, the adjustment of the convolution circle or the turned diameter, of the lathe tool is changed in dependence upon a rotational frequency or a centrifugal force. As the boring spindle is rotatable anyhow, the rotational frequency of the boring spindle can directly be used for changing or altering the effective convolution circle, that is, the working diameter of the lathe tool, because, to each definite rotational frequency, belongs also a definite centrifugal force, which can be brought into play for adjusting the convolution circle of the lathe tool. Consequently, it is possible, with a high degree of accuracy, to allocate to any optional frequency an exactly defined convolution circle.
It has been experimentally determined that by virtue of the features of the present invention, an extremely high working accuracy can be obtained. For example, it is possible, by applying the advantageous features of the method of the present invention, to machine pistons of an internal combustion engine in a circumferential direction and/or in a longitudinal direction with different working radii. In this manner, it is possible to machine a piston, for example, not only in a round fashion up to an approximate high degree of mathematical precision, but also over a circumference and/or length thereof in a crowned or oval manner.
Moreover, by virtue of the features of the present invention, the possibility exists to produce impressions with a very high degree of accuracy by changing the rotational frequency of the actuator at the circumference of the workpiece to be machined and/or in a longitudinal direction thereof in such a manner that the desired contour of the workpiece results in any given time.
The method of the present invention can be carried out in a simple manner by using a dynamically controlled motor driving the boring spindle and the actuator, respectively. Such motors are relatively poor in inertia so that they approximately change their speed of rotation and thus their rotational frequency in a manner similar to an oscillator at high revolutions such as 18,000 rpm after a few angular degrees of each rotation. Such a motor can be coaxially arranged to a boring bar or actuator and, in this manner, a construction is possible which enables a very compact design. Accordingly, to each rotational frequency is allocated a definite adjusting path of the lathe tool and therewith a definite diameter of the convolution circle.
As can be appreciated, the method of the present invention may, for example, not only be used for machining bores of piston bolts and peripheral surfaces of pistons but also for other purposes.
To enable an internal machining, in accordance with advantageous features of the device or apparatus of the present invention, a lathe tool, driven by a motor, is arranged in a tool holding fixture and driven through a boring bar or the like. For an internal working between the boring bar driven by a dynamically controlled motor and the lathe tool, at least a spring-resilient coupling member is inserted which, if necessary, indirectly takes up or accommodates the lathe tool and is deformable on a more or less large convolution circle in dependence upon a rotational frequency and of the centrifugal force, respectively.
In order to provide for an external machining, in accordance with advantageous features of another embodiment of the device or apparatus of the present invention, an adjusting system driven by a motor is provided for adjusting the lathe tool arranged in a tool holding fixture. For external working of workpieces between a shape resilient and a shape-stable coupling member receiving the lathe tool, in an actuator, at least one control lever is arranged which is controlled by a rotational frequency and a centrifugal force, respectively, with regard to a movement of the lathe tool.
By virtue of the above-noted features of the present invention, it is possible to provide a machine tool arrangement or construction which may be constructed in a solid manner at any given time and which only includes a few single parts so that the machine devices can be easily maintained. A lifting or raising of the lathe tool is not possible and a resilient coupling member, provided between the adjusting part and the lathe tool, is advantageously manufactured from a spring steel or from an elastic metallic material. The parts of the spring element or resilient coupling member are deformable with increasing rotational frequency and thus with increasing centrifugal force, whereby the lathe tool is accordingly adjusted across the respective boring bar.
In accordance with still further features of the present invention, a machining device apparatus is provided wherein the coupling member includes at least two spring parts diametrically opposed to each other and arranged in slot-like recesses of a boring bar in such a manner that the spring parts or ledges, at least at one end thereof, are removably connected to the boring bar by slotted cheese-head screws, while, at the other end or free end thereof, the ledges hold the lathe tool in a tool holding fixture across a longitudinal axis of the boring bar that projects at its one end from the tool holding fixture above the side limitation provided by the concerned spring ledge, whereby the tool holding fixture is provided coaxially to the recesses arranged in the spring ledges. A longitudinal portion of a distance sleeve is arranged in a bore opening into the recesses that is connected to a bore provided in the axial direction of the boring bar at one side. A double arm adjusting lever is adjustably arranged at a cylindrical pin with the double arm adjusting lever opening with a mass-rich end thereof into a central recess of the boring bar, whereby the adjusting lever with a short lever arm is actuatably connected to the spring ledges.
In accordance with still further features of the present invention, on each side of a longitudinal center line of the actuator is provided a control lever each of which is provided with a roller, with the control lever being connected to a common sleeve-like member which is adapted to embrace the actuator along a portion of a length thereof. Each of the control levers, at one end thereof is perfectly mounted about a respective bolt to a limited extent. The bolts, extend such that longitudinal axes thereof are parallel to each other and the respective rollers are rotatable around each axis that are parallel to the rotating axis of the bolts. The rollers are disposed adjacent to arcuate connecting slide links coupled through a bellow or deformable part with the boring bar. The boring bar is rotatably arranged with an extension member in a roller bearing accommodated in a basket-like adjusting part, to which a rod-like extension member is integrally connected, that supports itself through a thickening part against a shape-stable resilient coupling member which includes, for example, the two spring ledges and which is connected to a coupling part through a thread by a bolt-like extension so that the coupling part struts itself against the lathe tool, that is arranged in a bore being coaxial with the rod-like extension member of the shape stable coupling member.